The initial objective of this study was to identify serotypic differences by analysis of the nucleotides sequences of rotavirus stains representing different serotypes. Serotype-specific sequences were identified in the gene encoding the VP7 protein and a method for predicting rotavirus serotype from the nucleotide sequence was developed. The identification of serotype-specific sequences has proved to be useful in current studies which have the objectives of (a) developing "serotyping" assays using cloned DNA probes and/or oligonucleotides, (b) analyzing the immune response of individuals to serotypes-specific antigens on the VP7 and (c) determining the importance of naturally-occurring variants of each serotype in the epidemiology of rotavirus.